var CHAR_TILDE = 126;
var CODE_FNC1 = 102;
var SET_STARTA = 103;
var SET_STARTB = 104;
var SET_STARTC = 105;
var SET_SHIFT = 98;
var SET_CODEA = 101;
var SET_CODEB = 100;
var SET_STOP = 106;
var REPLACE_CODES = {
    CHAR_TILDE: CODE_FNC1 //~ corresponds to FNC1 in GS1-128 standard
}
var CODESET = {
    ANY: 1,
    AB: 2,
    A: 3,
    B: 4,
    C: 5
};

function getBytes(str) {
    var bytes = [];
    for (var i = 0; i < str.length; i++) {
        bytes.push(str.charCodeAt(i));
    }
    return bytes;
}

exports.code128 = function (ctx, text, width, height) {
    width = parseInt(width);
    height = parseInt(height);
    var codes = stringToCode128(text);
    var g = new Graphics(ctx, width, height);
    var barWeight = g.area.width / ((codes.length - 3) * 11 + 35);
    var x = g.area.left;
    var y = g.area.top;
    for (var i = 0; i < codes.length; i++) {
        var c = codes[ i ];
        //two bars at a time: 1 black and 1 white
        for (var bar = 0; bar < 8; bar += 2) {
            var barW = PATTERNS[ c ][ bar ] * barWeight;
            // var barH = height - y - this.border;
            var barH = height - y;
            var spcW = PATTERNS[ c ][ bar + 1 ] * barWeight;
            //no need to draw if 0 width
            if (barW > 0) {
                g.fillFgRect(x, y, barW, barH);
            }
            x += barW + spcW;
        }
    }
    ctx.draw();
}

function stringToCode128(text) {
    var barc = {
        currcs: CODESET.C
    };
    var bytes = getBytes(text);
    //decide starting codeset
    var index = bytes[ 0 ] == CHAR_TILDE ? 1 : 0;
    var csa1 = bytes.length > 0 ? codeSetAllowedFor(bytes[ index++ ]) : CODESET.AB;
    var csa2 = bytes.length > 0 ? codeSetAllowedFor(bytes[ index++ ]) : CODESET.AB;
    barc.currcs = getBestStartSet(csa1, csa2);
    barc.currcs = perhapsCodeC(bytes, barc.currcs);
    //if no codeset changes this will end up with bytes.length+3
    //start, checksum and stop
    var codes = new Array();
    switch (barc.currcs) {
    case CODESET.A:
        codes.push(SET_STARTA);
        break;
    case CODESET.B:
        codes.push(SET_STARTB);
        break;
    default:
        codes.push(SET_STARTC);
        break;
    }
    for (var i = 0; i < bytes.length; i++) {
        var b1 = bytes[ i ]; //get the first of a pair
        //should we translate/replace
        if (b1 in REPLACE_CODES) {
            codes.push(REPLACE_CODES[ b1 ]);
            i++ //jump to next
            b1 = bytes[ i ];
        }
        //get the next in the pair if possible
        var b2 = bytes.length > (i + 1) ? bytes[ i + 1 ] : -1;
        codes = codes.concat(codesForChar(b1, b2, barc.currcs));
        //code C takes 2 chars each time
        if (barc.currcs == CODESET.C) i++;
    }
    //calculate checksum according to Code 128 standards
    var checksum = codes[ 0 ];
    for (var weight = 1; weight < codes.length; weight++) {
        checksum += (weight * codes[ weight ]);
    }
    codes.push(checksum % 103);
    codes.push(SET_STOP);
    //encoding should now be complete
    return codes;

    function getBestStartSet(csa1, csa2) {
        //tries to figure out the best codeset
        //to start with to get the most compact code
        var vote = 0;
        vote += csa1 == CODESET.A ? 1 : 0;
        vote += csa1 == CODESET.B ? -1 : 0;
        vote += csa2 == CODESET.A ? 1 : 0;
        vote += csa2 == CODESET.B ? -1 : 0;
        //tie goes to B due to my own predudices
        return vote > 0 ? CODESET.A : CODESET.B;
    }

    function perhapsCodeC(bytes, codeset) {
        for (var i = 0; i < bytes.length; i++) {
            var b = bytes[ i ]
            if ((b < 48 || b > 57) && b != CHAR_TILDE)
                return codeset;
        }
        if (bytes.length % 2 == 0)
            return CODESET.C;
        else
            return CODESET.A;
    }

    //chr1 is current byte
    //chr2 is the next byte to process. looks ahead.
    function codesForChar(chr1, chr2, currcs) {
        var result = [];
        var shifter = -1;
        if (charCompatible(chr1, currcs)) {
            if (currcs == CODESET.C) {
                if (chr2 == -1) {
                    shifter = SET_CODEB;
                    currcs = CODESET.B;
                }
                else if ((chr2 != -1) && !charCompatible(chr2, currcs)) {
                    //need to check ahead as well
                    if (charCompatible(chr2, CODESET.A)) {
                        shifter = SET_CODEA;
                        currcs = CODESET.A;
                    }
                    else {
                        shifter = SET_CODEB;
                        currcs = CODESET.B;
                    }
                }
            }
        }
        else {
            //if there is a next char AND that next char is also not compatible
            if ((chr2 != -1) && !charCompatible(chr2, currcs)) {
                //need to switch code sets
                switch (currcs) {
                case CODESET.A:
                    shifter = SET_CODEB;
                    currcs = CODESET.B;
                    break;
                case CODESET.B:
                    shifter = SET_CODEA;
                    currcs = CODESET.A;
                    break;
                }
            }
            else {
                //no need to shift code sets, a temporary SHIFT will suffice
                shifter = SET_SHIFT;
            }
        }
        //ok some type of shift is nessecary
        if (shifter != -1) {
            result.push(shifter);
            result.push(codeValue(chr1));
        }
        else {
            if (currcs == CODESET.C) {
                //include next as well
                result.push(codeValue(chr1, chr2));
            }
            else {
                result.push(codeValue(chr1));
            }
        }
        barc.currcs = currcs;
        return result;
    }
}

//reduce the ascii code to fit into the Code128 char table
function codeValue(chr1, chr2) {
    if (typeof chr2 == "undefined") {
        return chr1 >= 32 ? chr1 - 32 : chr1 + 64;
    }
    else {
        return parseInt(String.fromCharCode(chr1) + String.fromCharCode(chr2));
    }
}

function charCompatible(chr, codeset) {
    var csa = codeSetAllowedFor(chr);
    if (csa == CODESET.ANY) return true;
    //if we need to change from current
    if (csa == CODESET.AB) return true;
    if (csa == CODESET.A && codeset == CODESET.A) return true;
    if (csa == CODESET.B && codeset == CODESET.B) return true;
    return false;
}

function codeSetAllowedFor(chr) {
    if (chr >= 48 && chr <= 57) {
        //0-9
        return CODESET.ANY;
    }
    else if (chr >= 32 && chr <= 95) {
        //0-9 A-Z
        return CODESET.AB;
    }
    else {
        //if non printable
        return chr < 32 ? CODESET.A : CODESET.B;
    }
}

var Graphics = function (ctx, width, height) {
    this.width = width;
    this.height = height;
    this.quiet = Math.round(this.width / 40);
    this.border_size = 0;
    this.padding_width = 0;
    this.area = {
        width: width - this.padding_width * 2 - this.quiet * 2,
        height: height - this.border_size * 2,
        top: this.border_size - 4,
        left: this.padding_width + this.quiet
    };
    this.ctx = ctx;
    this.fg = "#000000";
    this.bg = "#ffffff";
    // fill background
    this.fillBgRect(0, 0, width, height);
    // fill center to create border
    this.fillBgRect(0, this.border_size, width, height - this.border_size * 2);
}
//use native color
Graphics.prototype._fillRect = function (x, y, width, height, color) {
    this.ctx.setFillStyle(color)
    this.ctx.fillRect(x, y, width, height)
}
Graphics.prototype.fillFgRect = function (x, y, width, height) {
    this._fillRect(x, y, width, height, this.fg);
}
Graphics.prototype.fillBgRect = function (x, y, width, height) {
    this._fillRect(x, y, width, height, this.bg);
}
var PATTERNS = [
    [ 2, 1, 2, 2, 2, 2, 0, 0 ],  // 0
    [ 2, 2, 2, 1, 2, 2, 0, 0 ],  // 1
    [ 2, 2, 2, 2, 2, 1, 0, 0 ],  // 2
    [ 1, 2, 1, 2, 2, 3, 0, 0 ],  // 3
    [ 1, 2, 1, 3, 2, 2, 0, 0 ],  // 4
    [ 1, 3, 1, 2, 2, 2, 0, 0 ],  // 5
    [ 1, 2, 2, 2, 1, 3, 0, 0 ],  // 6
    [ 1, 2, 2, 3, 1, 2, 0, 0 ],  // 7
    [ 1, 3, 2, 2, 1, 2, 0, 0 ],  // 8
    [ 2, 2, 1, 2, 1, 3, 0, 0 ],  // 9
    [ 2, 2, 1, 3, 1, 2, 0, 0 ],  // 10
    [ 2, 3, 1, 2, 1, 2, 0, 0 ],  // 11
    [ 1, 1, 2, 2, 3, 2, 0, 0 ],  // 12
    [ 1, 2, 2, 1, 3, 2, 0, 0 ],  // 13
    [ 1, 2, 2, 2, 3, 1, 0, 0 ],  // 14
    [ 1, 1, 3, 2, 2, 2, 0, 0 ],  // 15
    [ 1, 2, 3, 1, 2, 2, 0, 0 ],  // 16
    [ 1, 2, 3, 2, 2, 1, 0, 0 ],  // 17
    [ 2, 2, 3, 2, 1, 1, 0, 0 ],  // 18
    [ 2, 2, 1, 1, 3, 2, 0, 0 ],  // 19
    [ 2, 2, 1, 2, 3, 1, 0, 0 ],  // 20
    [ 2, 1, 3, 2, 1, 2, 0, 0 ],  // 21
    [ 2, 2, 3, 1, 1, 2, 0, 0 ],  // 22
    [ 3, 1, 2, 1, 3, 1, 0, 0 ],  // 23
    [ 3, 1, 1, 2, 2, 2, 0, 0 ],  // 24
    [ 3, 2, 1, 1, 2, 2, 0, 0 ],  // 25
    [ 3, 2, 1, 2, 2, 1, 0, 0 ],  // 26
    [ 3, 1, 2, 2, 1, 2, 0, 0 ],  // 27
    [ 3, 2, 2, 1, 1, 2, 0, 0 ],  // 28
    [ 3, 2, 2, 2, 1, 1, 0, 0 ],  // 29
    [ 2, 1, 2, 1, 2, 3, 0, 0 ],  // 30
    [ 2, 1, 2, 3, 2, 1, 0, 0 ],  // 31
    [ 2, 3, 2, 1, 2, 1, 0, 0 ],  // 32
    [ 1, 1, 1, 3, 2, 3, 0, 0 ],  // 33
    [ 1, 3, 1, 1, 2, 3, 0, 0 ],  // 34
    [ 1, 3, 1, 3, 2, 1, 0, 0 ],  // 35
    [ 1, 1, 2, 3, 1, 3, 0, 0 ],  // 36
    [ 1, 3, 2, 1, 1, 3, 0, 0 ],  // 37
    [ 1, 3, 2, 3, 1, 1, 0, 0 ],  // 38
    [ 2, 1, 1, 3, 1, 3, 0, 0 ],  // 39
    [ 2, 3, 1, 1, 1, 3, 0, 0 ],  // 40
    [ 2, 3, 1, 3, 1, 1, 0, 0 ],  // 41
    [ 1, 1, 2, 1, 3, 3, 0, 0 ],  // 42
    [ 1, 1, 2, 3, 3, 1, 0, 0 ],  // 43
    [ 1, 3, 2, 1, 3, 1, 0, 0 ],  // 44
    [ 1, 1, 3, 1, 2, 3, 0, 0 ],  // 45
    [ 1, 1, 3, 3, 2, 1, 0, 0 ],  // 46
    [ 1, 3, 3, 1, 2, 1, 0, 0 ],  // 47
    [ 3, 1, 3, 1, 2, 1, 0, 0 ],  // 48
    [ 2, 1, 1, 3, 3, 1, 0, 0 ],  // 49
    [ 2, 3, 1, 1, 3, 1, 0, 0 ],  // 50
    [ 2, 1, 3, 1, 1, 3, 0, 0 ],  // 51
    [ 2, 1, 3, 3, 1, 1, 0, 0 ],  // 52
    [ 2, 1, 3, 1, 3, 1, 0, 0 ],  // 53
    [ 3, 1, 1, 1, 2, 3, 0, 0 ],  // 54
    [ 3, 1, 1, 3, 2, 1, 0, 0 ],  // 55
    [ 3, 3, 1, 1, 2, 1, 0, 0 ],  // 56
    [ 3, 1, 2, 1, 1, 3, 0, 0 ],  // 57
    [ 3, 1, 2, 3, 1, 1, 0, 0 ],  // 58
    [ 3, 3, 2, 1, 1, 1, 0, 0 ],  // 59
    [ 3, 1, 4, 1, 1, 1, 0, 0 ],  // 60
    [ 2, 2, 1, 4, 1, 1, 0, 0 ],  // 61
    [ 4, 3, 1, 1, 1, 1, 0, 0 ],  // 62
    [ 1, 1, 1, 2, 2, 4, 0, 0 ],  // 63
    [ 1, 1, 1, 4, 2, 2, 0, 0 ],  // 64
    [ 1, 2, 1, 1, 2, 4, 0, 0 ],  // 65
    [ 1, 2, 1, 4, 2, 1, 0, 0 ],  // 66
    [ 1, 4, 1, 1, 2, 2, 0, 0 ],  // 67
    [ 1, 4, 1, 2, 2, 1, 0, 0 ],  // 68
    [ 1, 1, 2, 2, 1, 4, 0, 0 ],  // 69
    [ 1, 1, 2, 4, 1, 2, 0, 0 ],  // 70
    [ 1, 2, 2, 1, 1, 4, 0, 0 ],  // 71
    [ 1, 2, 2, 4, 1, 1, 0, 0 ],  // 72
    [ 1, 4, 2, 1, 1, 2, 0, 0 ],  // 73
    [ 1, 4, 2, 2, 1, 1, 0, 0 ],  // 74
    [ 2, 4, 1, 2, 1, 1, 0, 0 ],  // 75
    [ 2, 2, 1, 1, 1, 4, 0, 0 ],  // 76
    [ 4, 1, 3, 1, 1, 1, 0, 0 ],  // 77
    [ 2, 4, 1, 1, 1, 2, 0, 0 ],  // 78
    [ 1, 3, 4, 1, 1, 1, 0, 0 ],  // 79
    [ 1, 1, 1, 2, 4, 2, 0, 0 ],  // 80
    [ 1, 2, 1, 1, 4, 2, 0, 0 ],  // 81
    [ 1, 2, 1, 2, 4, 1, 0, 0 ],  // 82
    [ 1, 1, 4, 2, 1, 2, 0, 0 ],  // 83
    [ 1, 2, 4, 1, 1, 2, 0, 0 ],  // 84
    [ 1, 2, 4, 2, 1, 1, 0, 0 ],  // 85
    [ 4, 1, 1, 2, 1, 2, 0, 0 ],  // 86
    [ 4, 2, 1, 1, 1, 2, 0, 0 ],  // 87
    [ 4, 2, 1, 2, 1, 1, 0, 0 ],  // 88
    [ 2, 1, 2, 1, 4, 1, 0, 0 ],  // 89
    [ 2, 1, 4, 1, 2, 1, 0, 0 ],  // 90
    [ 4, 1, 2, 1, 2, 1, 0, 0 ],  // 91
    [ 1, 1, 1, 1, 4, 3, 0, 0 ],  // 92
    [ 1, 1, 1, 3, 4, 1, 0, 0 ],  // 93
    [ 1, 3, 1, 1, 4, 1, 0, 0 ],  // 94
    [ 1, 1, 4, 1, 1, 3, 0, 0 ],  // 95
    [ 1, 1, 4, 3, 1, 1, 0, 0 ],  // 96
    [ 4, 1, 1, 1, 1, 3, 0, 0 ],  // 97
    [ 4, 1, 1, 3, 1, 1, 0, 0 ],  // 98
    [ 1, 1, 3, 1, 4, 1, 0, 0 ],  // 99
    [ 1, 1, 4, 1, 3, 1, 0, 0 ],  // 100
    [ 3, 1, 1, 1, 4, 1, 0, 0 ],  // 101
    [ 4, 1, 1, 1, 3, 1, 0, 0 ],  // 102
    [ 2, 1, 1, 4, 1, 2, 0, 0 ],  // 103
    [ 2, 1, 1, 2, 1, 4, 0, 0 ],  // 104
    [ 2, 1, 1, 2, 3, 2, 0, 0 ],  // 105
    [ 2, 3, 3, 1, 1, 1, 2, 0 ]   // 106
]

